Fluid contact coking of hydrocarbon oils, fines recirculation improvement



Oct. 28, 1958 MADINGER 2,858,253

FLUID CONTACT COKINE; 0F HYDROCARBON OILS, FINES RECIRCULATION IMPROVEMENT Filed Dec. 1, 1954 2,858,253 Patented Oct. 2%, 1958 hoe FLUID CONTACT COKING OF HYDROCARBON OILS, FINES RECIRCULATION IMPROVEMENT Hulit L. Madinger, Eastchester, N. Y., assignor to The Texas Company, New York, N. Y., a corporation of Delaware Application December 1, 1954, Serial No. 472,461

3 Claims. (Cl. 20228) This invention relates to the cracking and coking of hydrocarbon o-ils by contacting with highly heated powdered or pulverulent coke under fluidized conditions and pertains to a process in which the coke particles are withdrawn from the cracking and coking reactor and subjected to combustion to burn a portion of the coke and the hot coke returned to the reactor. It is found that in such a process there is a tendency as the run proceeds for the build-up in the system of coke particles of increased size. The enlarged particles interfere with proper fluidization and may cause agglomeration and plugging of the system. In accordance with the present invention the coarser coke is selectively withdrawn from the reactor-burner cycle so as to maintain in the system coke of proper sizes for fluidization.

In practicing the invention coke in the reactor-burner cycle, preferably down stream from the coke burner, is subjected to classification to separate the coarser particles and the separated coarser coke is removed from the cycle.

The selective removal of the coarser coke from the circulating coke stream may be accomplished in various ways. In one method a settling vessel is provided in the transfer line between the coke burner and the reactor and coke collecting in the separator is fluidized in a gaseous stream under conditions to maintain a dilute phase and a dense phase with the coarser particles being concentrated in the dense phase and coke is withdrawn from the dense phase while the coke in the dilute phase is returned to the system.

In another method of selectively removing the coarser coke, coke in the transfer line from the burner to the reactor is conducted to a centrifugal classifier or cyclone wherein the coarser particles are separated from the finer ones.

The invention is more specifically described herein by reference to a method of classifying the coke particles by gaseous elutriation and reference is had to the accompanying drawing which is a diagrammatic elevational view of apparatus constructed in accordance with the invention and constituting an embodiment thereof.

The apparatus includes a reactor in which the hydrocarbon oil is subjected to cracking and coking in contact With fluidized coke and a burner 11 in which the coke is subjected to combustion to provide the heated coke for the cracking and coking of the oil. Charge oil, such as reduced crude or other heavy residual stock, is introduced through a line 12 thence through one or more branch lines disposed at different levels in the reactor such as 12a, 12b and 120, being discharged through nozzles 13 into contact with the fluidized coke. Steam or gas for establishing and maintaining fluidization is admitted by means of a ring pipe 14 having a plurality of inlets to the coke chamber. The evolved vapors and gases pass to a separator or cyclone 15 thence to a vapor line 16 by which they are conducted to suitable fractionating equipment (not shown).

Coke is withdrawn from the dense phase in the reactor through a line 17 to a transfer line 18 into which air or oxygen containing gasis admitted by a line 19. The introduction of the air produces a dispersion of the coke and subjects it to burning. The mixture of air and coke undergoing burning is discharged from the line 18 through a distributor 20 into the coke burner or separator 11 wherein fluidized conditions are maintained. The resultant flue gases leave the burner and separator through a cyclone 21. and flue 22. Coke descends from the dense phase in the coke burner and is conducted by a conduit 23 to the dense phase of the reactor 10.

A portion of the coke flowing in line 23 is withdrawn and conducted by a line 24 to a classifier or elutriator 25. Steam or other gaseous medium admitted through distributor 26 fluidizes the coke particles in the chamber 25 with the resultant formation of a dense phase and a dilute phase therein. The coarser particles are concentrated in the dense phase and are removed by a line 27 from the system constituting the product coke of the process. The finer coke particles are removed in the steam or other gases and are conducted by a line 28 to the reactor 10, preferably being introduced to the lower portion of conduit 23 to assist in the delivery of the coke to the reactor.

By continuously withdrawing a minor portion of the coke flowing in line 23, separating the finer coke from coarser coke and Withdrawing the coarser coke from the system the build-up of coke of too large a size for fluidization is effectually prevented and good fluidization conditions are continuously maintained in the reactor. The particle size of coke adapted for fiuidization will vary considerably with the size'of the equipment and with steam or gas rates but it may be stated that good fluidization conditions can ordinarily be maintained with coke particles of about 30-200 mesh.

The usual temperatures employed in fluid contact coking such as of the order of 900 F. and 1.000" F. are employed in the process with preferably relatively low pressures such as about 10 p. s. i. g., although higher pressures may be used if desired.

Obviously, many modifications and variations of the invention, as hereinbefo-re set forth, may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

I claim:

1. In the fluid contact coking of hydrocarbons oils wherein the oil is contacted in a reaction zone with coke under fluidized conditions at cracking and coking temperatures, coke is withdrawn from the reaction zone and subjected to combustion, and resultant highly heated coke is recycled through a transfer line to the reaction zone, the process that comprises withdrawing a portion of said highly heated coke from said transfer line, subjecting the withdrawn highly heated coke to a classifying operation to separate finer coke from coarser coke, withdrawing the separated coarser coke from the system and returning the finer coke to said reaction zone.

2. In the fluid contact coking of hydrocarbon oils wherein the oil is contacted in a reaction zone with coke under fluidized conditions at cracking and coking temperatures, coke is withdrawn from the reaction zone and subjected to combustion in a burning zone, and resultant highly heated coke is recycled through a transfer line to the reaction zone, the method of controlling the particle size of the circulating coke that comprises withdrawing a portion of the coke flowing in said transfer line, subjecting the withdrawn coke to gaseous elutriation to form a dense phase in which the coarser coke is concentrated and a dilute phase containing finer particle sized coke, directing the dilute phase constituents to the reac tion zone and withdrawing the dense phase constituents from the system.

3. In the fluid contact coking of hydrocarbon oils wherein the oil is contacted in a reaction zone with coke under fluidized conditions at cracking and coking temperatures, coke is withdrawn from the reaction zone and subjected to combustion, and rcsultant highly heated coke is recycled through a transfer line to the reaction zone, the process that comprises withdrawing a portion .of said highly heated coke from said transfer line, subjecting the 7 withdrawn highly heated coke to centrifugal classification to separate finer coke from coarser coke, withdrawing the separated coarser coke from the system and returning the finer coke to said reaction zone.

References Cited in the file of this patent UNITED STATES PATENTS 2,421,212 Medlin May 27, 1947 4 Schutte et a1 June 10, Jahnig Nov. 18, Schutte Dec. 23, Clouse et a1. Jan. 6, Brown et al. Oct. 13, Kollgaard Oct. 27, Letter Dec. 1, Matheson July 13, Borgerson et a1. Jan. 11, Watson May 3, Matheson et a1. June 21, Moser Feb. 14, Molstedt, et al Feb. 21, Martin Oct. 30, 

1. IN THE FLUID CONTACT COKING OF HYDROCARBONS OILS WHEREIN THE OIL IS CONTACTED IN A REACTION ZONE WITH COKE UNDER FLUIDIZED CONDITIONS AT CRACKING AND COKING TEMPERATURES, COKE IS WITHDRAWN FROM THE REACTION ZONE AND SUBJECTED TO COMBUSTION, AND RESULTANT HIGHLY HEATED COKE IS RECYLED THROUGH A TRANSFER LINE TO THE REACTION ZONE, THE PROCESS THAT COMPRISES WITHDRAWING A PORTION OF SAID HIGHLY HEATED COKE FROM SAID TRANSFER LINE, SUBJECTING THE WITHDRAWN HIGHLY HEATED COKE TO A CLASSYFYING OPERATION TO SEPARATE FINER COKE FROM COARSER COKE, WITHDRAWING THE SEPARATED COARSER COKE FROM THE SYSTEM AND RETURNING THE FINER COKE TO SAID ZONE. 